Shaped like a giant baseball bat, the 700-ton FLIP, or Floating Instrument Platform, is a Navy barge operated by Scripps Institution of Oceanography in San Diego. Once towed to a site, the vessel flips to vertical. "It was built in 1962 to refine acoustic targeting for submarine rockets, but scientists quickly realized that it would be useful for all kinds of research," says Bill Gaines, FLIP's program director. "So 45 years later, FLIP still serves the oceanographic community." And it is still one of a kind.

Stability

Tanks 5, 8 and 9, and parts of tanks 6 and 7, remain filled with air to keep FLIP buoyant. Like the Louisville Slugger that the vessel was modeled from, FLIP increases in diameter from bow to stern -- a profile that contributes to its stability when vertical. "A design criterion for FLIP was that it move less than one-tenth of a passing wave's height," Gaines says.

Staying in place

Three nylon lines, each connected to a chain and anchor weighing a total of 9 tons, maintain FLIP's position. For some research projects, however, FLIP is allowed to drift unmoored -- on one occasion, for 150 miles.

Power

Though it has no propulsion, FLIP has a small, hydraulically operated thruster that can rotate the vessel and maintain a heading. FLIP also has three diesel generators that supply 340 kilowatts of power. These ride high above the water so that they don't contaminate acoustic data collected by FLIP's underwater sensors.

Orientation

The engines, large galley equipment and bunks are mounted on trunnions, allowing the vessel to rotate around them, and then are locked into place with pins. Every room has a door in both the wall and ceiling, and there are two showers­ -- one for the boat's horizontal position and one for its vertical.

Flipping back

Reorienting to horizontal takes only half as long, but involves twice as many steps as the vertical flip. Up to 3000 cu. ft. of compressed air, stored at 250 psi, is blown into the ballast tanks -- pushing water back out through the flood openings. The operator floods tank 9B so that the keel remains down as the vessel swings back to the surface.

Ocean science

FLIP's stability and soundlessness make it an ideal platform for listening to ocean acoustics; hydrophones can detect anything from whale calls to underwater earthquakes. One recent find: the sound of all-night fish choruses as loud as fans in a stadium stomping their feet. Other sensors, lowered from the deck by booms and winches, can measure temperature, wave height and water density. Doppler sonar deployed along FLIP can pinpoint the motion inside waves with an accuracy of one centimeter per second in a cubic kilometer of ocean. "It's hard to measure wiggly things, like waves, from a ship that's bouncing," says Robert Pinkel, a physical oceanographer at Scripps. "I've spent a couple of years total on FLIP over the course of my life -- it's been a godsend."

Horizontal22.5º45ºVertical
The operator floods tanks 7B, 3B and part of 1T. The actual flip begins as 6B fills with water. Tanks 1B, 2 and 4 are open to the ocean and flood quickly; controlled flooding of tanks 1T and 3T slows the descent.

FLIP passes through a point of instability, and then begins to move faster. Flooding of tank 6 is usually stopped at half-full; its level varies according to the amount of cargo.

The vessel is ballasted; all flooding stops. FLIP races through the next 45 degrees at speeds of 3.5 mph vertically and 6 mph laterally.

FLIP hits vertical, bobs and spins in several clockwise 360s. The operator equalizes the water level between the two halves of tank 7 to ensure the vessel is plumb.